This invention generally relates to a methane storage device to store methane emitted into an air induction system of an engine in an automobile.
The emission standard limits the, amount of hydrocarbons, carbon dioxide and particulate matter that can be emitted from the vehicle""s tailpipe. Due to laws requiring the reduction of the levels of hydrocarbons that vehicles may emit into the atmosphere, it is necessary for automotive designers to consider alternate fuel technology to control emissions. One such alternate fuel technology that has been developed is the use of natural gas to run vehicles.
Natural gas which contains primarily over 70% methane is one of the cleanest fuels known in the automotive industry. Natural gas is used on vehicles as compressed natural gas (CNG), as the gas is compressed at over 3000 psi and stored in a fuel cylinder aboard the vehicle. Exhaust emissions from Natural Gas Vehicles (NGV) are much lower than those from equivalent gasoline-powered vehicles. For instance, NGV emissions of carbon monoxide are approximately 70% lower, non-methane organic gas emissions are 89% lower, and oxides of nitrogen emissions are 87% lower. In addition to these reductions in pollutants, NGVs also emit significantly lower amounts of greenhouse gases and toxins than gasoline vehicles do.
Although tailpipe emissions are significantly lower for NGV, hydrocarbons including methane are released from the engine, even when the engine is not operating. Hydrocarbons, primarily methane remaining from engine reactions can leak out of the engine through the engine""s air intake systems. Although such emissions are not as significant as the tailpipe emissions, it is desirable to reduce the amount of methane leaked from the air intake systems as methane is known to cause green house effect.
Typically, hydrocarbons emitted from the engine""s air intake system are controlled by placing a hydrocarbon adsorbing material in the air intake tube. Typically these hydrocarbon adsorbing materials are formed from carbon or zeolite and are capable of adsorbing most of the hydrocarbons released by the engine. However, methane has a very low efficiency of storage in hydrocarbon adsorbing materials. This low efficiency of storage is primarily due to the non reactive nature of the methane molecule. Although it may be possible to store methane in these hydrocarbon adsorbing materials it requires expensive processes.
Therefore there is a need in the automotive industry, primarily NGV""s to reduce the amount of evaporative methane released from the engine""s air intake system. According, there is a need to find solutions where methane can be stored at atmospheric pressure at or near room temperature.
In one aspect of the invention, an air induction system of an automotive internal combustion engine comprises a methane storage device for storing evaporative methane emitted by the engine. In yet another aspect of the present invention, the methane storage device is connected to the air intake tube of the air induction system.
In yet another aspect of the present invention, the methane storage device has a housing having an interior chamber. The interior chamber is substantially filled with a reticulated material that is capable of trapping methane.
In yet another aspect of the present invention, the housing is provided with an inlet port to introduce methane inside the interior chamber. The housing is also provided with an outlet port to purge the methane vapors to the engine.
In yet another aspect of the present invention, a method of trapping methane in the air induction system is provided.